Hormonal influences on growth of B16 murine melanoma.

The influence of endocrine factors on B16 melanoma growth was investigated in young and old male mice to test the hypothesis that senescent hormonal changes account for the age-associated reduced tumor growth previously observed in our laboratory. Again it was demonstrated that tumors grow more slowly and to a lesser volume in old mice. For a test of whether senescent hormonal changes account for this tumor growth pattern, B16 was implanted into male and female C57BL/6 mice and tumor growth observed. In addition, young adult male mice were castrated and later B16 melanoma growth was determined. Tumor growth was similar in male and female mice. Contrary to our expectations, however, castrated male mice demonstrated larger tumor volumes, despite serum testosterone levels similar to those of old mice. Furthermore, after iv tumor cell injection, the occurrence of pulmonary colonies was greater in castrated mice. These observations indicate the importance of hormonal factors in this commonly explored tumor system. With regard to aging and tumor growth, however, senescent sex hormone changes probably do not account for the slower tumor growth observed in aged animals.